Frequency control for oscillation generators



. Nov. 3,1931. A. McL. NICOLSON 1,830,329

FREQUENCY CONTROL FOR OSCILLATION GENERATORS Filed Aug. 23, 1927 2 Sheets-Sheet l rmzunvcx Mamas f Fig. 2

FEE Ql/EA/C Y INCREASE WORK CJRCU IT INVENTOR ALEXANDER McLEAN [HCOLSON e 3. a 2%;

TORN EY Nov. 3, 1931. A, MCL, go 1,830,329

FREQUENCY CONTROL FOR OSCILLAT ION GENERATORS Filed Aug. 25, 1927 2 Sheets-Sheet 2 I worm Z CIRCUIT J 4.4 7 T /7 7%: 2 12 m 16 ,4 I

INVENTOR ALEXANDER Mc LEAN NICOLSON ATTORNEY QPa tnted 11931 j oFFIce ic nsees mc rso bpmw om, N.Y., AssIeNomBY nsnn ASSIGN- nrnnrs rornnnnnnrnnnenarnoomrnnv, A conr'osnrron or CALIFORNIA HEREQUENCY conrnor. iron osoILLA'rIon GENERATORS Application 'filed AuguSt ZS, 19 27. I Serial No. 214,888.

"Thisinvention relates to electrical oscilla- 1 tion generators, and'more particularly to such generators utilizing OIIBDI; more thermionic vacuum tubes, provided with a plurality of.

' piezoeelectric crystal devices, and one or more:

i tuningelements, constructed: and arranged to j generate electrical oscillations, the frequency "of which maybe determined by the adjustment ofthe tuning controls in such manner 1c?- that the apparatus will generate oscillations of one of, a plurality of frequencies correspending to the-particular response charac- V teristics of the crystals utilized.

It is an'objectof this invention toprovide relatively simple and-eflicient apparatus of,

the class described, which isreadilyi-controL lable to select the frequency of 'the'oscillations desired, and whichwill'roscillate at-an ex tremely constant frequency at any one'of the.

r 293 natural frequencies 'afi'orded by the :appalratus.'-=Sti-ll other objectsa-n'd advantages of my invention will be apparent from the speci-; 'fication. :';-j Y j The featuresofnovelty which I believe to 9 be characteristic ofmy invention are set forth with; particularity in"-'the appended claims.

. Y My invention itself, however, both as to; its fundamental principlesand as to its part cular embodiments will best'be understood by 7307 reference'to the specification and accompany ing drawings, in which q q. I p

, Figures 1, 2 and 3 arecurves explain ng the 'operation thereof.

F igures; 4, 5, 6 and 7 are diagrammatic views of various-forms of circuitsinaccordan'ce-Withmy invention.

It is well known that pieZo-electric crystal ,devicessuc'h as slabs of; quartz, tourmaline,-

Rochelle saltea'nd the like, are capable of vi-" brati-ng in responsetoelectrical stresses impressed thereon and, conversely, 1f vlbrated mechanically, produce electrical stresses.

communication. It has. been the custom in v to each frequency desired/ In addition, 1

-.to change-such devices when. it is desired tochangev the, frequency of oscillations tobe generated In accordance" with my invention, I provide a plurality'of'suchdevices. associated with the thermionic'amplifi'er in ajmalnner to feed back energy from the output circuit thereof to the input circuit, to-

sustain the oscillationsproduced. The, crys 70 tall devices will preferably be so chosen that,

their natural frequencies of oscillation are different and that some oneof the crystal de.-'

viceshas a: natural frequency corresponding 75 provide one or more tuning devices for selecting. the natural frequency of oscillations desired. The frequency selecting means may, and preferably will, be a series or parallel tuned circuit or circuits associated with the Q 1 crystaldevice anawah either the input or.

output circuit of the amplifier, or with both the input andv output circuits; and operative to select approximately the frequency of oscillation desired, and the piezoelectric device or devices having a natural frequency of vibrations most closely corresponding. to the; tuning of the tuning means control and determine the frequency exactly. If the device is operating at one frequency, and it is desiredto change-over to another frequency,

' it is only necessary to vary the tuning means "Since the frequency characteristic of vibra so that the tuning of the circuit is changed to correspond to another of the natural frequen cies of vibration of the crystal device which will, in turn, set or control the frequency of the oscillations generated-l By this means it is; possibleqto provide anoscillator which will produce oscillations of any oneof a number m, of frequencies covering a. desired band and aelectric crystal, and as will. be noted,- this.

terv'als.

Referring now more particularly to Figure 1, the curve therein shown may represent the response character stic of a particular piezocrystalm'ay have response' peaks at frequencies a, o and e,'due to vibration in different mod-es, orother causes.) If used alone ina 'ie of these frequencies, dependingupon a number of conditions.

control isprovided, it isjpossibleto cause the If, however, some tuning crystal to vibrate at anyone of its natural haveresp'onse peaks at frequenciesb, d and f and, if utilized alone, this crystal device Would oscillate at one ofsaidfrequencies 'depending upon conditions. r By theuse of a tuningdevice, the frequency desired may be selected. 5 V .c If new, two such devices be utilized in the "same circuit, it Wlll be understood that thev responsepeaks of both of-themmay be'util-s iZed; and oscillations may 'begenerated' at 7 anyone of" the frequencies a, 6,0, d, e and f, an appropriate tunmgmeans bGlIlgPIOVlflGd V for the purposeof selectingthe particular frequency, It Will be understood that while havereferred to the use of two devices, my invention is notlimitedthereto, but contemplates'the use ofthreeor more of such devices,

having different frequency characteristics,

by means of which afconsiderably greater number of frequencies-maybe generated than in the' case of-a single such device. 1 o

1 "It is to be notedithat'the exact position of the responsepeaks maybe displaced'lslightly when the crystalsare v associated-together,

dueto the mutual effect of each crystal. on

' the other, in a manner analogous to the effect of; two resonant currents'on eachother when tic l nk 13.

coupled. l l V Referring now more particularly to Figure 4, I designate a thermionic amplifier system, herein'shown diagrammatically as a single vacuum tube amplifier of the type commonly usedI in'the art; but actually comprising as 4 iiianystages of preferably aperiodic amplification asrmay be necessary or desired,-and

comprising an evacuated vessel having therein a cathode 2 adapted to emit electrons, an 7 anode 5 andaeontrol electrode or grid 4.

The cathodejmay be heated to electron-emitingtemperatureby any suitable means, such. as battery 3. 'The'output circuit, connected between the anode 5 and the cathode 2, com

prises an inductance 6 shunted by variable capacityt), and a suitable source of potential 7; Inductively coupled with the coil 6 is a lations'generated to a suitable work circuit,

such as a radio transmitter or the like. The inductance of the coil and its coupling with the coil 6, are preferably made variablerto ob tain' optimum adjustments-z The energy impressed upon the coil 6. is transferred to piezo-electric crystal device- 10 provided with conducting metallic poles 10a and 10b, and

having the usual electrodes l' l and 12, which circuit, without any; frequency selecting are connected'to; the free terminals ofconmeans,ithe crystal might vibrate at any one" denser 9 and coilf8 and to the cathode 2-respectively. Achoke 22 is provided connected in shunt withelectrodes'll and 12' Associ- ,ated with the piezo-electric crystal device 10,

I provide a second piezoelectric crystal de- VlCOll, havingapair of electrodes 15 and 16,

and also having. metal poles 14a and 'l lb.

The electrode 16 may be connected to the cathode circuit and the electrode=15 is connected directly to the control electrode 4;. The crystal devices 10 and 14 are mechanically associated or coupled by being in this instance,laid one upon theother, -'In operation, the energy impressed on crystallO causes vibrations thereof, which vibrationsare transmitted mechanically to crystal 14,, and cause the generation of potential difierences corresponding thereto, which are impressed on the control circuit of the amplifiersystem, and thereby repeated inzthe output circuit setting up continuous oscillations, the frequency of which is deter- I minedbyithe tuning Dirt/118 output circuit, as well as by other factors, such frequencies "of both crystals; ,1

' Referring now more particularly .to Fig as the natural ure 5, Ighave showniaislightly different ar rangement, in which the Crystal 10 isqinduc tivelycoupled' to the amplifier output coil 6,

s by meansofa series tuned circuit comprising inductance l9 and variable capacity 9, andin WlllCli a series tuned input circuit comprising inductance 17 and variable capacity 18 is utilized fortuning the input-circuit; The

mechanical coupling or energy transfer con nection is shown diagrammatically as an elase While I have shownthe connection13 di-c agrannnatically as a link, it will be understood thatin'practice this connection may be obtained in a number of ways. a For example, thevcrystals may be mounted on a common mountingplate having sufiicient elasticity to transmitvibrations from the oneto the other, or again, the crystals maybe directly associated, as for example,-'being laid, as shown in Fig. 4, oneagainstthe other.- Under certain conditions, also, the mechanical coupling may take theform of-an actual link ofel'astic material connecting the crystal devices, r

. ,Apick-up coil 8-may be associated inductively with the coils 6 =and,:19, andmaylead V to a suitable work circuit 20, which may coniprise an amplifier, modulator and radiotransmitter or the like, 1 a f 5 '25 frequency, and the system will operate to a result in the production of beats, which might will be seen, iustas in Fig. 4, that by reason of the mechanical connection between I the crystals and14, the vibrations occurring in the one are transmitted tothe, other,

as if thecrystal devices 10 and 14 were one and the same, having a frequency characteristic representing the sum of theiindividual characteristics of the two, separate devices slightly modified by the mutual effect of each" vibration at some one of its natural frequencies to which the output circuit is tuned.

The electrical oscillationsimpressed upon the crystal device 10 cause mechanical vibrationsthereof, wh ch are in turn communicated to the crystal device lewd the forced vibrations of this device cause the generation of corresponding oscillations upon the electrodes 15 and 16; By tuning the input circuit, comprising inductance 17 and capacity system is a minimum at the particular de- 18 to this frequency, the impedance of the circuit is made a minimum to this partlcular generate oscillations of selected frequency.

In case it is desired to change the frequency,

the tuning of the circuits will be correspondinglychanged, 'so that the impedance of the V jsired frequency,which may be a naturalfrequency of crystal device 10, or ofv crystal device 14.- a

' additional frequencies of operation.

Referring now moreparticularly toFigure 6, I have shown an additional crystal devicev 14a in parallel with crystal device. 14, giving It may be pointed out in this connection that if any two piezo-electriccrystal de ices I beselected at random, their natural frequenfcieswill not ordinarily correspond, since in order to obtain crystal'devlces whose natural crystals arematched. In case of a slight defrequencies are the same, it is necessary that the dimensions, shapes and materials ofthe crystals be very carefully chosen, so that the viation, even in one dimension of the crystals from each other, the response characteristics will be different.

In this connection, it should also be noted, that it is preferable to use crystals which have sufficien'ly different response characteristics,

so that the system will not oscillate on the two frequencies simultaneously, which would 1 interfere with the desired operation.

I series tuned'circuit, and also utilizing conductive coupling of the crystal device 10 to the output circuit of the amplifier 1, similar 7 to Fig. 4. In this arrangement, inductance 6 is included in the plate circuit of the amplifier 1, and is also connected in series with variable condenser 9 to electrodes of the piezoelectric crystal device 10.

While I-have shown and described certain preferred embodiments of my invention, it will be understood that modifications and changes may be made, Wl-lllOllt departing from the spirit and scope of my invention, as will be understood by those skilled in the art.

1. An electrical oscillatory system, the combination of an electron tube having grid, filament and plate electrodes, an input circuit interconnecting said grid and filament electrodes, an output circuit interconnecting said plate and filament electrodes, and a plurality of piezo eleccric crystals mechanically associated each having selected constant frequenp ate and filament electrodes, and a. plurality of piezo-electric crystals each having selected constant frequency oscillaory characteristics one of said crystals being connected in said input circuit and another of said crystals in said output circuit for controlling the generation of oscillations in accordance with the frequency of a selected one of said piezo-electric crystals.

3. In, a frequency control or stabilizing system a multiplicity of piezo-electric crystals. of different frequency characteristics mechanically associated and separated one H from another, an electron tube circuit having an input circuit connected to one of said crystals and an output circuit connected to anotherof said crystals, and means connected with-said electron tube circuit for selectively sustaining the oscillations of any one of said crystals at its characteristic frequency.

Signed at New York city in the county of New York and State of New York this 11th day of August, A. D. 1927.

ALEXANDER MoLEAN NICOLSON. 

